Matrix Style Log Formatter

## Overview

We all know that distributed programming is hard.

The current console logger is pretty handy, but for development info logging it's pretty tough to make sense of the output, after all there is only one STDOUT and many threads. -- and all the log messages are displayed sequentially.

This PR adds a new sidekiq config option:

```
:logformat: matrix
```

It uses a different logger formatter to print the single letters to STDOUT offet by the index of the current thread in Thread.list.

## Example

```
                           i
d                           i
                           i
                           i
                 s
                 d
                    s
                    d
d                           d
dddd   s
d    s
dd     s
                    s
                 s
ddddddddddddddddd    d
dddd                           s
ddd                   d
    s
d     i
     d
                   s
                    i
                   i
                   d
     s
     d
                   s
                    d
```

This may not look like much to the untrained eye, but all I see is "success, failure, job milestone 1, etc"

I considered doing this much cooler in with curses, but since my project is Jruby that was not really an option.